Reduced moisture compositions comprising an acid gas and a matrix gas, articles of manufacture comprising said compositions, and processes for manufacturing same

ABSTRACT

Compositions comprising a reactive gas and a matrix gas are disclosed, as well as articles of manufacture and methods of making the articles. The methods of manufacturing preferably employ zeolites to remove moisture from the reactive gas and from the matrix gas, and then combine the moisture reduced gases either in a container, or prior to filling a container, which has been previously vacuum-baked and passivated. The invention produces stable standard gas compositions having improved shelf-life.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to non-provisional patent application Ser.Nos. 10/______, 10/______, and 10/______, all filed concurrentlyherewith on May 29, 2002, all of which are incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is generally related to the field of manufacturingcompositions comprising an acid gas and a matrix gas having reducedmoisture, and which are stable in acid gas concentration for more thanan insignificant time period. The invention is also related to articlesof manufacture containing these compositions, such as metal cylinderscontaining the compositions, ton units containing the compositions, andthe like.

2. Related Art

Moisture is known to react with reactive gases, such as the so-called“acid gases”, for example, hydrogen sulfide, carbonylsulfide,carbondisulfide and mercaptans (mercaptans are also referred to asthiols) to form a complex compound. (The term “acid gas” is used hereinto denote either gas phase, liquid phase, or mixture of gas and liquidphases, unless the phase is specifically mentioned.)

One problem presents itself: if one is interested in producing reactivegas standard compositions, in other words reactive gases having a knownconcentration of one of these gases in a matrix or carrier fluid, thenone must consider how to reduce or remove the moisture. Gas standardsmay have to have, and preferably do have, a long shelf life, since thestandard reactive gas may not be required immediately after production.A source of reactive gas may contain a considerable amount of moisture.Therefore, the reduction or removal of moisture from the reactive gas isof primary importance if the stability of the reactive gas in thestandard gas is to be maintained. It has also recently been observedthat moisture in the matrix gas (prior to its being mixed with the acidgas) contributes to the problem, for if one removes moisture from thereactive gas, and then mixes the dried reactive gas with a wet matrixgas, the problem has not been entirely solved, even if the moisturelevel in the matrix gas is comparatively low.

A second, related problem involves the containers that the reactive gasstandards are stored in. If metal or metal lined, reactive gases willreact with and/or become adsorbed onto the metal, and will ultimatelychange the concentration of the reactive gas.

Grossman et al. (U.S. Pat. No. 4,082,834) describes alloys, such asalloys of nickel, titanium, and zirconium, that react with water andreactive gases (such as hydrogen, hydrogen-containing compounds such ashydrocarbons, carbon monoxide, carbon dioxide, oxygen, and nitrogen) attemperatures ranging from about 200° C. to about 650° C. While thepatent does not discuss acid gases, it is apparent that hydrogensulfide, carbonyl sulfide, and mercaptans are hydrogen-containingcompounds, so that there would not be any expected benefits using thesealloys to remove moisture from these acid gases. While carbondisulfidedoes not contain hydrogen, and therefore there could be some moisturereduction from a composition comprising carbondisulfide and moistureusing these alloys, the high temperature is prohibitive for commercialuse.

Tamhankar et al. (U.S. Pat. No. 4,713,224) describes a one-step processfor removing minute quantities of impurities from inert gases, where theimpurities are selected from the group consisting of carbon monoxide,carbon dioxide, oxygen, hydrogen, water and mixture thereof. The processcomprises contacting the gas with a particulate material comprised ofnickel in an amount of at least about 5% by weight as elemental nickeland having a large surface area, from about 100 to about 200 m 2/g.There is no disclosure of removal of moisture from reactive gases; thereis therefore no discussion or suggestion of moisture removal fromreactive gases, moisture removal from matrix gases and mixing same toform a standard gas composition.

Tom et al (U.S. Pat. Nos. 4,853,148 and 4,925,646) discloses processesand compositions for drying of gaseous hydrogen halides of the formulaHX, where X is selected from the group consisting of bromine, chlorine,fluorine, and iodine. The patent describes the use of, for example, anorganometallic compound such as an alkylmagnesium compound, on asupport. The halide is substituted for the alkyl functional group.Suitable supports are, alumina, silica, and aluminosilicates (natural orsynthetic). However, there is no description or suggestion of reducingor removing moisture from sulfur-containing reactive gases, or ofremoval of moisture from matrix gases and mixing the reduced moisturegases to form a standard gas. Alvarez, Jr. et al. (U.S. Pat. No.5,910,292) describes a process and apparatus for removal of water fromcorrosive halogen gases, using a high silica zeolite, preferably highsilica mordenite. The patent describes removing moisture down to lessthan or equal to 100 ppb water concentration in halogen gases,particularly chlorine- or bromine-containing gases, but once again,there is lacking any teaching of suggestion of standard gascompositions. U.S. Pat. No. 6,183,539 discloses utilizing high sodium,low silica faujasite particles for the adsorption of carbon dioxide andwater vapor from gas streams. The disclosed types of gas streams inwhich this type of high sodium, low silica faujasite crystals can beutilized includes air, nitrogen, hydrogen, natural gas, individualhydrocarbons and monomers, such as ethylene, propylene, 1,3 butadiene,isoprene and other such gas systems. There is no mention ofsulfur-containing acid gas purification using the faujasites, orproduction of standard gas compositions.

U.S. Pat. No. 4,358,627 discloses use of “acid resistant” molecularsieves, such as that known under the trade designation “AW300”, forreducing the chloride concentration in chlorinated liquid hydrocarbonsthat contain an ethylenically unsaturated chlorinated hydrocarbon, waterand hydrogen chloride. The method includes providing certainnitrogen-containing compounds in the system and contacting the systemwith the molecular sieve. There is no disclosure or suggestion, however,of removal or reduction of moisture from gas phase compositions, orproduction of standard gas compositions.

Given the problems of moisture reacting with sulfur-containing acidgases and other reactive gases, and the fact that some or all reactivegases will react with metals, there is a definite and unmet need forstandard gas compositions, articles of manufacture including thosestandards which are stable over reasonable periods of time, and methodsof producing same.

SUMMARY OF THE INVENTION

The present invention overcomes many if not all of the problems notedabove. In accordance with the present invention, certain “acid gasresistant” molecular sieve compositions are employed to reduce or removemoisture from fluid compositions comprising a reactive gas (preferablyan acid gas, preferably a sulfur-containing acid gas), and moisture isremoved from a matrix gas using the same or different means. The reducedmoisture reactive gas and reduced moisture matrix gas are then combined,either prior to entering a vacuum-baked, “passivated” container, oradded to the vacuum-baked, passivated container in succession, or addedsimultaneously (for example through separate valves) where mixing takesplace in the container. As used herein the term “remove” means that thewater content of the final composition comprising the reactive gas willbe equal to or less than 100 parts per billion (ppb), more preferablyless than 10 ppb, and more preferably less than 1 ppb. As used hereinthe term “reduced” means that the moisture concentration of the finalcomposition comprising the reactive gas will be no more than 0.1 timesthe starting fluid composition water concentration, preferably no morethan 0.01 times, and more preferably no more than 0.001 times thestarting moisture concentration. Presently, the detection limit formoisture is about 4 ppm in reactive gases comprising a sulfur-containingcompound. Compositions are made to 4 ppm concentration, then diluted tothe desired reduced moisture concentration. As used herein the term“sulfur-containing compound” includes carbondisulfide, carbonylsulfide,and compounds within formula (I):Y—S—X  (I)

-   -   wherein        -   S is sulfur,        -   X and Y are the same or different and are independently            selected from the group consisting of hydrogen, alkyl, aryl,            oxygen, and alcohol.            Examples of preferred sulfur-containing compounds within            formula (I) include hydrogen sulfide, sulfur dioxide,            methylthiol, ethylthiol, n-propylthiol, i-propylthiol,            benzylthiol, and the like.

In accordance with the present invention, methods of passivatinginternal surfaces of containers that have been cleaned and vacuum-bakedare employed to increase the shelf-life of gas compositions, especiallylow concentration reactive gas products. As used herein the term“shelf-life” means that time during which the initial concentration of areactive gas stored in a container is substantially maintained at theintended or desired concentration. In this context, the phrase“substantially maintained” means that for concentrations of about 1000parts per billion (ppb), the reactive gas concentration does not vary bymore than +/−10 percent; for concentrations of about 500 ppb, theconcentration does not vary by more than +/−15 percent; forconcentrations of about 100 ppb, the concentration does not vary by morethan +/−20 percent. “Low concentration” reactive gases means gaseshaving a concentration in another gas, such as inert gas or matrix gas,of 1000 ppb or less.

The passivated internal metal surface of the container comprises (1) thereaction product of a silicon-containing material and anoxygen-containing material (preferably selected from the groupconsisting of moisture, molecular oxygen, metal oxides, and mixturesthereof), and (2) an effective amount of the reactive gas, the effectiveamount being many times the intended concentration of reactive gas thatis to be substantially maintained. Preferred articles of manufacture ofthe invention include products wherein the passivated internal surfaceis a passivated metal. Preferably the metal is selected from the groupconsisting of aluminum, aluminum alloys, steel, iron and combinationsthereof. Yet other preferred manufactured products of the invention arethose wherein the silicon-containing material is selected from the groupconsisting of compounds within the general formula (II):SiR¹R²R³R⁴  (II)wherein R¹, R², R³, and R⁴ are the same or different and areindependently selected from the group consisting of hydrogen, halogen,amine, alkyl, aryl, halogenated alkyl, and halogenated aryl; andmanufactured products wherein the compound is silane or amethyl-containing silane, more preferably wherein the methyl-containingsilane is selected from the group consisting of methylsilane,dimethylsilane, trimethylsilane and tetramethylsilane.

Reactive gases which benefit from the passivation techniques of thepresent invention include nitrous oxide, nitric oxide, hydrogenchloride, chlorine, boron trichloride, and any acid gases except thosethat would react with a silicon-containing compound.

A first aspect of the invention are compositions comprising a reactivegas (preferably an acid gas, preferably a sulfur-containing compound)and a matrix gas, wherein the sulfur-containing compound has aconcentration in the composition of no more than 1 part per million(ppm) in the matrix gas, and the composition has a moistureconcentration of no more than 100 ppm, preferably no more than 10 ppm,more preferably no more than 1 ppm. Preferred compositions are thosewherein the reactive gas is selected from the group consisting ofnitrous oxide, nitric oxide, hydrogen chloride, chlorine, borontrichloride, and any acid gases except those that would react with asilicon-containing compound, including sulfur-containing compoundsselected from the group consisting of carbondisulfide, carbonylsulfide,and compounds within formula (I).

A second aspect of the invention are articles of manufacture comprising:

-   -   a) a container having an internal space and a passivated        internal metal surface;    -   b) a composition of the first aspect of the invention contained        within the internal space and in contact with the passivated        internal metal surface, the reactive gas having an intended        concentration that is substantially maintained; and    -   c) the passivated internal metal surface comprising:        -   1) the reaction product of a silicon-containing material and            an oxygen-containing material (preferably selected from the            group consisting of moisture, molecular oxygen, metal            oxides, and mixtures thereof), and        -   2) an effective amount of the reactive gas, the effective            amount being many times the intended concentration of            reactive gas that is to be substantially maintained.

Preferred articles of manufacture of the invention are those wherein thereactive gas is selected from those mentioned in the first aspect of theinvention. Other preferred articles of manufacture include productswherein the passivated internal surface is a passivated metal.Preferably the metal is selected from the group consisting of aluminum,aluminum alloys, steel, iron and combinations thereof. Yet otherpreferred manufactured products of the invention are those wherein thesilicon-containing material is selected from the group consisting ofcompounds within the general formula (II).

Preferred articles of manufacture of the invention are those wherein thecomposition comprises a reactive gas having a concentration of about1000 ppb and that does not vary by more than +/−10 percent; productswherein the composition comprises a reactive gas having a concentrationof about 500 ppb and that does not vary by more than +/−15 percent;products wherein the composition comprises a reactive gas having aconcentration of about 100 ppb and that does not vary by more than +/−20percent. Products wherein the composition comprises higher or lowerconcentration of reactive gas, and correspondingly larger or smallervariation in concentration, are considered within the invention.

Preferred articles of manufacture of the invention comprise only asingle reactive gas with an inert gas like nitrogen, argon, helium, andthe like. The composition may comprise a mixture of two or more reactivegases. Also, the balance of the fluid composition is, in some preferredembodiments, a hydrocarbon, such as ethylene, propylene, and the like.

A third aspect of the invention are methods of making articles ofmanufacture of the invention, the methods comprising the steps of:

-   -   i) reducing the moisture content of a reactive gas (preferably        an acid gas, preferably a sulfur-containing gas) using an        acid-gas resistant molecular sieve, to form a reduced moisture        reactive gas;    -   ii) reducing the moisture content of a matrix gas using means        for moisture reduction, to form a reduced moisture matrix gas;    -   iii) vacuum baking an internal metal surface of a container        (preferably including any metal sufaces of metal valves attached        to the container) at a temperature ranging from about 30° C. to        about 75° C. for no less than 1 hour (preferably no less than 6        hours, more preferably no less than 12 hours), at a vacuum no        more than 100 torr, preferably no more than 1 torr, and more        preferably no more than 0.01 torr, to form a vacuum-baked        internal metal surface of the container;    -   iv) exposing the vacuum-baked internal metal surface of the        container to a first fluid composition comprising a        silicon-containing compound for a time sufficient to allow at        least some of the silicon-containing compound to react with        oxygen-containing compounds (preferably selected from the group        consisting of moisture, molecular oxygen, metal oxides, and        mixtures thereof) present to form a silicon-treated surface on        at least some of the vacuum-baked internal metal surface of the        container, the silicon-containing compound preferably selected        from the group consisting of compounds within the general        formula (II);    -   v) evacuating the container for a time sufficient to remove        substantially all of the silicon-containing compound(s) that has        not reacted with the oxygen-containing compounds to form the        silicon-treated surface;    -   vi) exposing the silicon-treated surface to a second fluid        composition, the second fluid composition comprising a reactive        gas having a concentration that is greater than an intended        reactive gas concentration of the article of manufacture;    -   vii) evacuating the container for a time sufficient to remove        just enough of the second fluid composition to enable        maintenance of an increased shelf-life, low concentration        reactive gas at the intended concentration in the container; and    -   viii) combining at least a portion of the reduced moisture        reactive gas with at least a portion of the reduced moisture        matrix gas to form an intended gas composition in the container.

Preferred methods in this aspect of the invention are those wherein thesilicon-containing compound is selected from the group consisting ofsilane, methylsilane, dimethylsilane, trimethylsilane andtetramethylsilane. Also preferred are methods wherein the second fluidcomposition has a concentration of reactive gas at least 10 times theintended reactive gas concentration of the manufactured product; methodswherein steps iv) and v) are repeated prior to step vi); methods whereinthe metal surface is cleaned prior to step iii); methods wherein theconcentration of the silicon-containing compound used in step vi) rangesfrom about 100 ppm to 100 percent; and methods wherein during step vii)the second composition is heated to a temperature of not more than 75°C. Other preferred methods are those wherein the container is a gascylinder having an attached cylinder valve, and the cylinder valve isremoved prior to step iv). After steps i)-vi) are completed, preferablyat very high temperatures for steps iv) and vi, the cylinder valve isreattached, and the process steps iv)-vi) are repeated, but steps iv)and vi) take place at not more than 75° C.

Preferred acid gas-resistant molecular sieve is selected from the groupconsisting of molecular sieves having an effective pore size rangingfrom about 1 Angstrom up to about 10 Angstroms, more preferably rangingfrom about 3 to about 8 Angstroms. Preferred are the molecular sievesknown under the trade designations AW300 and AW500, particularly hereinthe molecular sieve is AW300.

Preferably, moisture removal steps within the invention are carried outat combinations of temperature and flow rate that will ensure water inthe fluid will not freeze, and where the reactive gas will notdecompose. Preferred temperatures range from just above 0° C. to justbelow a temperature where the reactive gas will decompose. Temperaturesbelow 0° C. are disfavored because of the possibility of water freezingin the container, or in the molecular sieve pores, or both. Temperaturesabove the decomposition temperature of the reactive gas during moistureremoval are disfavored due to possible decomposition of the reactivegas. It may be possible, through increased flow rate (or decreasedresidence time) conditions in the container, to operate below 0° C. orexceed the decomposition temperature briefly. Generally, it is preferredto operate at reduced temperature, as the acid gas resistant molecularsieve materials seem to operate more efficiently at these temperatures.

Further aspects and advantages of the invention will become apparent byreviewing the description of preferred embodiments that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a logic diagram illustrating the methods of the invention;

FIG. 2 is a graph illustrating moisture removal data from hydrogensulfide (reactive gas) in one embodiment of the invention; and

FIG. 3 illustrates stability data for a standard mixture of 1 ppm H₂S,which had been previously de-moisturized as described in reference toFIG. 2, mixed with a purchased ethylene matrix gas originally having 1ppm moisture, and after vacuum-baking an aluminum cylinder at 65° C. ata vacuum of 1 torr for 6 hours.

DESCRIPTION OF PREFERRED EMBODIMENTS

Adsorption of moisture from fluid compositions comprising moisture andsulfur-containing compounds may be evaluated through several theories,with the exception that such theories do not recognize the benefits ofuse of an acid gas-resistant molecular sieve. The degree of adsorptionof moisture onto the acid gas-resistant adsorbent depends in acomplicated way on the chemical and physical properties of theadsorbent, the temperature and pressure employed during this step, aswell as on the chemical and physical properties of the particularsulfur-containing fluid from which moisture is being removed. Theseparameters are in turn dictated by the final concentration of moisturein the sulfur-containing fluid that is to be produced.

A discussion of adsorption of gaseous species onto surfaces that ishelpful in this respect is included in Daniels, F. et al., “ExperimentalPhysical Chemistry”, Seventh Edition, McGraw-Hill, pages 369-374 (1970).While the inventors are not certain, it is believed that the attractionof the reactive gas to the coating is physical in nature, involving aninteraction of dipoles or induced dipoles, but may be chemical in natureinvolving chemical bonds, as when oxygen is adsorbed on charcoal. Acombination of physical and chemical forces may be at work as well.

As stated in Daniels, et al., infra, experimental data for adsorptionmay be plotted as adsorption isotherms, in which the quantity of gasadsorbed (expressed as milliliters at 0° C. and 760 mm) per gram ofadsorbing material is plotted against the equilibrium pressure. In manycases of adsorption it is possible to relate the amount of adsorbedmaterial to the equilibrium pressure, using the empirical equation ofFreundlich,V=kP ^(n)where

-   -   V=number of milliliters of gas, corrected to 0° C. and 760 mm,        adsorbed per gram of adsorbing material;    -   P=pressure; and    -   k and n are constants that may be evaluated form the slope and        intercept of the line obtained when log V is plotted against log        P.

Alternatively, Langmuir considered adsorption to distribute moleculesover the surface of the adsorbent in the form of a unimolecular layer.Consideration of the dynamic equilibrium between adsorbed and freemolecules leads to the following relation:P/V=P/V _(u)+1/kV _(u)Where P and V are as defined previously, V_(u) is the volume of gas 0°C., 760 mm adsorbed per gram adsorbent when unimolecular layer iscomplete, and k is a constant characteristic of the adsorbent-adsorbatepair. Thus, if P/V is plotted against P, a straight line is obtained ifthe Langmuir equation applies. The slope of the line is equal to 1/Vu;when the line is extrapolated to low pressures, as P goes to 0, P/Vapproaches the finite limit 1/kVu. The values of the constant s may alsobe obtained by plotting 1/V versus 1/P. By postulating the building upof multimolecular adsorption layers on a surface, Brunauer, Emmett, andTeller extended the Langmuir derivation for unimolecular layeradsorption to obtain an isotherm equation for the more complicated case.Thus, the surface area of a coating produced by the practice of thepresent invention may be determined by the B.E.T. method, and preferablyis at least about 1 m²/gram, more preferably at least 10 m²/gram. If thecoating is somewhat porous, the pore volume may be determined bynitrogen adsorption isotherm methods, and is preferably at least 0.1ml/gram. The B.E.T. method is described in detail in Brunauer, S. Emmet,P. H., and Teller, E., J. Am. Chem. Soc., 60, 309-16 (1938). Thenitrogen adsorption isotherm method is described in detail in Barrett,E. P., Joyner, L. G. and Helenda, P. P., J. Am. Chem. Soc., 73, 373-80(1951), incorporated by reference herein.

As stated previously, the term “remove” means that the water content ofthe final composition comprising the sulfur-containing compound will beequal to or less than 100 ppb, more preferably less than 10 ppb, andmore preferably less than 1 ppb. (As noted previously, these moistureconcentrations are not presently measurable directly, but are obtainedby dilution.) As used herein the term “reduce” means that the moistureconcentration of the final composition comprising the sulfur-containingfluid will be no more than 0.1 times the starting fluid compositionwater concentration, preferably no more than 0.01 times, and morepreferably no more than 0.001 times the starting moisture concentration.

The acid gas resistant molecular sieves useful in the invention aretypically and preferably those described in Ameen et al. (U.S. Pat. No.4,358,627), incorporated by reference herein. Preferred are the acid gasresistant molecular sieves known under the trade designations AW 300 andAW 500, available from Universal Oil Products (UOP). The effective poresize of the molecular sieve known under the trade designation AW 300 isabout 4 Angstroms, and the effective pore size of the molecular sieveknown under the trade designation AW 500 is about 5 Angstroms. Adiscussion of the acid gas resistant molecular sieves may be found inCollins, J. J., “A Report on Acid-Resistant Molecular Sieve Types AW-300and AW-500”, Oil and Gas Journal, Dec. 2, 1963, which is incorporatedherein by reference. Such molecular sieves are available as pellets ofdiameters of about one eighth inch and one sixteenth inch.

As stated in U.S. Pat. No. 4,358,627, molecular sieves are crystallinemetal alumino-silicates. The molecular sieves are basically a3-dimensional framework of SiO₄ and AlO₄ tetrahedra, the tetrahedrabeing cross-linked by the sharing of oxygen atoms so that the ratio ofoxygen atoms to the total of the aluminum and silicon atoms is equal to2. The electro valance of the tetrahedra containing aluminum is balancedby the inclusion in the crystal of a cation, for example an alkali oralkaline earth metal ion. One cation may be exchanged for another by ionexchange techniques, which are known. The spaces between the tetrahedraare occupied by water molecules prior to dehydration. The dehydrationresults in crystals interlaced with channels of molecular dimensionsthat offer very high surface areas for the adsorption of foreignmolecules. In addition, the term “molecular sieve” as used in thepresent disclosure contemplates not only aluminosilicates, but alsosubstances in which the aluminum has been partly or wholly replaced,such as for instance by gallium and/or other metal atoms, and furtherincludes substances in which all or part of the silicon has beenreplaced, such as for instance by germanium. Titanium and zirconiumsubstitution may also be practiced. Most molecular sieves, or zeolitesas they are also referred to, are prepared or occur naturally in thesodium form, so that sodium cations are associated with the electronegative sites in the crystal structure. However, the molecular sievemay be ion exchanged. Suitable cations for replacement of sodium in themolecular sieve crystal structure include ammonium (decomposable tohydrogen), hydrogen, rare earth metals, alkaline earth metals, and thelike. Various suitable ion exchange procedures and cations which may beexchanged into crystal structure are well known to those skilled in theart. Examples of the naturally occurring crystalline aluminosilicatezeolites which may be used or included in the present invention arefaujasite, mordenite, clinoptilote, chabazite, analcite, erionite, aswell as levynite, dachiardite, paulingite, noselite, ferriorite,heulandite, scolccite, stibite, harmotome, phillipsite, brewsterite,flarite, datolite, gmelinite, caumnite, leucite, lazurite, scaplite,mesolite, ptholite, nepheline, matrolite, offretite and sodalite.Examples of the synthetic alumino-silicate zeolites which are useful forcarrying out the present invention are Zeolite X, U.S. Pat. No.2,882,244, Zeolite Y, U.S. Pat. No. 3,130,007; and Zeolite A, U.S. Pat.No. 2,882,243; as well as Zeolite B, U.S. Pat. No. 3,008,803; Zeolite D,Canada Pat. No. 661,981; Zeolite E, Canada Pat. No. 614,495; Zeolite F,U.S. Pat. No. 2,996,358; Zeolite H, U.S. Pat. No. 3,010,789; Zeolite J,U.S. Pat. No. 3,001,869; Zeolite L, Belgian Pat. No. 575,177; Zeolite M,U.S. Pat. No. 2,995,423, Zeolite O, U.S. Pat. No. 3,140,252; Zeolite Q,U.S. Pat. No. 2,991,151; Zeolite S, U.S. Pat. No. 3,054,657, Zeolite T,U.S. Pat. No. 2,950,962; Zeolite W, U.S. Pat. No. 3,012,853, Zeolite Z,Canada Pat. No. 614,495; and Zeolite Omega, Canada Pat. No. 817,915.Also ZK-4HJ, alpha beta and ZSM-type zeolites are useful. Moreover, thezeolites described in U.S. Pat. Nos. 3,140,249, 3,140,253, 3,044,482 and4,137,151 are also useful, the disclosures of said patents beingincorporated herein by reference.

Referring now to FIG. 1, there is illustrated schematically a logicdiagram for carrying out methods of the invention. A container having ametal internal surface is selected at 12. The metal surface is vacuumbaked, in step 13, at temperatures ranging from about 30° C. to about75° C., at reduced pressure, preferably no more than 100 torr, morepreferably no more than 1 torr, more preferably no more than 0.01 torr,for a time of no less than 1 hour, preferably no less than 6 hours, andmore preferably no less than 12 hours. This forms a vacuum-bakedinternal metal surface, which is then exposed to a silicon-containingpassivation material, 14, for a time and at a temperature and pressuresufficient to react most of the silicon-containing material withoxygen-containing compounds present on the metal surface. Step 14individually is a known passivation technique, typically combined withnitrogen baking, and needs little explanation to the skilled artisan.See for example “Wechter on Stable Pollution Gas Standards”, p. 44, ASTM(1976). The container is then evacuated for a time sufficient to removethe bulk of the non-reacted silicon-containing material, at 16. Next,the metal surface is exposed to high concentration of reactive gas orliquid of the desired end product to be contained in the container, at18. Step 18 is also known as an alternative passivation technique toStep 14, and needs little explanation to the skilled artisan. See“Wechter on Stable Pollution Gas Standards”, p. 43-44, ASTM (1976). Thecontainer is again evacuated at 20 for a time sufficient to removesubstantially all of the non-adsorbed reactive gas. The container isthen ready to be filled at 22, either with the composition having thedesired material at the desired concentration of moisture and reactivegas, or with a reduced moisture matrix gas and a reduced moisturereactive gas, or first with a reduced moisture matrix gas and then witha reduced moisture reactive gas, or first with a reduced moisturereactive gas and then with a reduced moisture matrix gas. At this point,the container is allowed to equilibrate and the concentration of the gasin the container is tested at various times to determine theconcentration of reactive gas in the container. If the shelf life isacceptable at 24, the product is made in accordance with the procedurefollowed, at 26. If the concentration of the gas increases or decreasesbeyond the accepted tolerances, then the process of steps 20, 22, and 24are repeated. Optionally, steps 14 and 16 may be repeated, as indicatedat 26.

Moisture may be removed from reactive gases as taught in co-pending Ser.No. ______, filed simultaneously with the present application. Theco-pending application describes an apparatus comprising a fluid inletend, a fluid outlet end, a container, and an acid gas resistantmolecular sieve contained within an internal space within container. Thecontainer may take any shape required by the user, includingcylindrical, kidney shaped, spiral wound, and the like. Preferably thecontainer is cylindrical. The fluid outlet end may have a connection toa conduit which preferably routes some or all of the effluent fluid,reduced in moisture content, to a means for moisture measuring,preferably a diode laser-based sensor, as described in U.S. Pat. Nos.5,880,850; 5,963,336; and 6,154,284, all incorporated herein byreference. Such sensors typically include one or more diode lasersources, temperature control circuits, and the like, and a spectroscopiccell through which the diode laser passes through and encounters all ora portion of the gas sample being analyzed. Through an analysis of theabsorbed radiation by the species of interest, in this case moisture,the concentration of the species of interest may be determined. Similarapparatus and moisture sensors are preferably employed to removemoisture from matrix gases. In practice, a source of reactive gas, suchas a tank or truck trailer, or other source of fluid such as cylinder orton unit are provided. A ton unit may be a source liquid or a source ofgas. In any case, fluid comprising a reactive gas and moisture enter ameans for removing moisture as described in reference to co-pendingapplication Ser. No. ______. The means for moisture removal may have aspare unit or units installed in parallel. A bypass conduit allows onecontainer to be taken out of service and replaced, if necessary. Fluiddepleted in moisture exits the container, and then is either mixed withthe reduced moisture matrix gas, or delivered straight to thevacuum-baked, passivated container. Optionally, the moisture-depletedreactive fluid may be passed through a downstream treatment unit, whichis preferably a unit that removes particulate matter that may haveescaped from the molecular sieve. An optional temperature control unitis preferred. As a general rule, the acid gas resistant molecular sievesseem to work more efficiently at cooler temperatures (25° C. and lower),although one must be careful not to freeze the moisture being removed.Also, there may be temperatures above 25° C. at which chemisorptioncontributes significantly to the overall adsorption, due to higherkinetic rate constants at higher temperatures. However, as temperatureis increased even more, this effect will tend to be overcome by thephysical desorption of moisture from the molecular sieve.

The means for maintaining the molecular sieve in the container is amaterial that is substantially inert to the acid gas. Preferably, themeans for maintaining the molecular sieve in the container is themolecular sieve material itself contacting an inner surface of thecontainer. For economic reasons, it may be preferred to hold the acidgas-resistant molecular sieve in a secondary or material inside thecontainer, such as with end screens in the fluid entrance and exit endsmade from porous metals such as stainless steels, aluminum, VCRconnections, gaskets, frits, and the like. Further it may be preferredto mix the acid gas-resistant molecular sieve with one or more non-acidgas-resistant materials, preferably another molecular sieve material. Itis within the invention to use more than one container, either inparallel or series arrangement in terms of flow of feed fluid. Forexample, it may be desired to have a series arrangement, where thesecond or succeeding containers have the same or different molecularsieve materials. In parallel arrangements, it is preferred to have twocontainers with the same molecular sieve in each container, and toeffect flow in one container while the other container is beingregenerated, such as by heating, contacting with dry fluid, orcombination of these. Such parallel and series arrangements are known inthe adsorption art, for example, the air separation field.

Reduced moisture compositions of the invention preferably comprising areduced moisture reactive gas and a reduced moisture matrix gas, thecompositions comprising at least one reactive gas having a reactive gasconcentration and a moisture concentration, the moisture concentrationbeing no more than 0.1 times the concentration of the reactive gas inthe matrix gas. Fluid compositions may either have one reactive gas, ormore than one. If more there are two reactive gases, the molar ratio ofthe two may range from about 1:99 to about 99:1, more preferably fromabout 20:80 to about 80:20, and more preferably ranging from about 40:60to about 60:40. Examples of fluid compositions considered within theinvention include a mixture of carbonylsulfide and hydrogen sulfide in anitrogen matrix gas, the molar ratio of carbonylsulfide to hydrogensulfide ranging from about 20:80 to about 80:20; mixtures of hydrogensulfide and methylthiol (otherwise known as methyl mercaptan) in anitrogen matrix gas, with molar ratio of hydrogen sulfide to methylthiolranging from about 20:80 to about 80:20, and the like.

During the moisture removal steps, the flow rate of the fluid comprisingmoisture (either a reactive gas or a matrix gas) will be sufficient tocreate a space velocity preferably of at least one container volume perminute, more preferably at least about 5 container volumes per minute.It is also possible, although not preferred, to mix moist reactive gaseswith moist matrix gases, and then remove the moisture from both thereactive gas and the matrix gas simultaneously. However, it is believedto be more controllable, and therefore more preferable, to removemoisture separately from reactive gases and matrix gases. The spacevelocity of course will depend on the temperature of the feed fluid, theamount of moisture in the feed fluid, the flow pattern through theapparatus of the invention. If the fluid is gaseous, higher temperaturesand higher flow rates will tend to create more difficulty in removingmoisture from the fluid, as the volume of the fluid will tend to belarger and there will be less contact time. Conversely, in general lowertemperatures and lower feed rates will be beneficial in removing moremoisture. The feed pressure is not critical, but it should not be sohigh as to render the pressure drop through the container too high, lestthe molecular sieve be damaged. Preferably, a means for filtering theproduct fluid is provided (downstream of the molecular sieve) to filterout and particles of molecular sieve that may break away form the mainportion.

FIG. 2 is a graph illustrating moisture removal data from hydrogensulfide in one embodiment of the invention. The apparatus comprised 14grams of the molecular sieve known under the trade designation AW300,which had flowing there through a gas stream comprising hydrogen sulfideand from about 60 to about 80 ppm of moisture. The test was conducted atroom temperature (about 20° C.). The flow rate of the gas stream throughthe molecular sieve was 1 liter/minute. The moisture in the streamexiting the apparatus was measured using a diode laser measurementsystem, such as described in U.S. Pat. Nos. 5,880,850; 5,963,336; and6,154,284, previously incorporated herein by reference, although othermeans for moisture analysis could be used as well. As may be seen in thedata of FIG. 2, the molecular sieve worked extremely well in reducingthe moisture level of the hydrogen sulfide stream.

Additional experiments were performed on sulfur dioxide streams, andsimilar moisture removal abilities were observed.

FIG. 3 illustrates 38 days of stability data for a standard mixture of 1ppm H₂S, which had been previously de-moisturized as described inreference to FIG. 2, mixed with a purchased ethylene matrix gas(ethylene purity 99.99995, from Special Gas Services originally having 1ppm moisture), and after vacuum-baking an aluminum cylinder at 65° C. ata vacuum of 1 torr for 6 hours. As may be seen, the stability of themixtures are quite good after this time period. Although this data wasobtained using purchased ethylene matrix gas having a reduced moisture,it is expected that the same or very similar results would be obtainedupon using a “wet” mixture of a reactive gas with a matrix gas, and thende-moisturizing the mixture and placing the de-moisturized mixture intoa passivated container in accordance with the invention, or takingseparate sources of “wet” reactive gas and “wet” matrix gas,de-moisturizing each separately, then mixing in a passivated container.

Although the description herein is intended to be representative of theinvention, it is not intended to limit the scope of the appended claims.

1. A composition of matter comprising a reactive gas and a matrix gas,wherein the reactive gas has a concentration in the composition of nomore than 1 part per million in the matrix gas, and the composition hasa moisture concentration of no more than 100 ppm.
 2. The composition ofclaim 1 wherein the reactive gas comprises an acid gas.
 3. Thecomposition of claim 2 wherein the acid gas comprises asulfur-containing compound.
 4. The composition of claim 2 wherein theacid gas is selected from the group consisting of nitrous oxide, nitricoxide, hydrogen chloride, chlorine, boron trichloride, and any acidgases except those that would react with a silicon-containing compound.5. The composition of claim 3 wherein the sulfur-containing gas isselected from the group consisting of carbondisulfide, carbonylsulfide,and compounds within formula (I):Y—S—X  (I) wherein S is sulfur, X and Y are the same or different andare independently selected from the group consisting of hydrogen, alkyl,aryl, oxygen, and alcohol.
 6. The composition of claim 5 wherein thesulfur-containing gas is selected from the group consisting of hydrogensulfide, sulfur dioxide, methylthiol, ethylthiol, n-propylthiol,i-propylthiol, and benzylthiol.
 7. The composition of claim 1 whereinthe moisture content is no more than 10 ppm.
 8. The composition of claim1 wherein the moisture content is no more than 1 ppm.
 9. The compositionof claim 1 wherein the moisture content is no more than 10 ppb.
 10. Thecomposition of claim 1 wherein the moisture content is no more than 1ppb.
 11. An article of manufacture comprising: a) a container having aninternal space and a passivated internal metal surface; b) a compositionof claim 1 contained within the internal space and in contact with thepassivated internal metal surface, the reactive gas having an intendedconcentration that is substantially maintained; and c) the passivatedinternal metal surface comprising: 1) the reaction product of asilicon-containing material and an oxygen-containing material, and 2) aneffective amount of the reactive gas, the effective amount being manytimes the intended concentration of reactive gas that is to besubstantially maintained.
 12. The article of manufacture of claim 11wherein the reactive gas has a concentration of about 1000 ppb, and theconcentration does not vary by more than +/−10 percent.
 13. The articleof manufacture of claim 11 wherein the reactive gas has a concentrationof about 500 ppb, and the concentration does not vary by more than +/−15percent.
 14. The article of manufacture of claim 11 wherein the reactivegas has a concentration of about 100 ppb, and the concentration does notvary by more than +/−20 percent.
 15. The article of manufacture of claim11 wherein the oxygen-containing material is selected from the groupconsisting of moisture, molecular oxygen, metal oxides, and mixturesthereof.
 16. The article of manufacture of claim 11 wherein thepassivated metal is selected from the group consisting of aluminum,aluminum alloys, steel, iron and combinations thereof.
 17. The articleof manufacture of claim 11 wherein the silicon-containing material isselected from the group consisting of compounds within the generalformula (II):SiR¹R²R³R⁴  (II) wherein R¹, R², R³, and R⁴ are the same or differentand are independently selected from the group consisting of hydrogen,halogen, amine, alkyl, aryl, halogenated alkyl, and halogenated aryl.18. The article of manufacture of claim 17 wherein thesilicon-containing compound is selected from the group consisting ofsilane, dimethylsilane, trimethylsilane, tetramethylsilane, and mixturesthereof.
 19. The article of manufacture of claim 111 wherein the matrixgas is selected from the group consisting of nitrogen, argon, helium,and mixtures thereof.
 20. The article of manufacture of claim 11comprising a mixture of two or more reactive gases in a matrix gas. 21.The article of manufacture of claim 11 wherein the gas compositioncomprises a hydrocarbon.
 22. A method of making an article ofmanufacture, the method comprising the steps of: i) reducing themoisture content of a reactive gas using an acid-gas resistant molecularsieve, to form a reduced moisture reactive gas; ii) reducing themoisture content of a matrix gas using means for moisture reduction, toform a reduced moisture matrix gas; iii) vacuum baking an internal metalsurface of a container (preferably including any metal surfaces of metalvalves attached to the container) at a temperature ranging from about30° C. to about 75° C. for no less than 1 hour (preferably no less than6 hours, more preferably no less than 12 hours), at a vacuum no morethan 100 torr, preferably no more than 1 torr, and more preferably nomore than 0.01 torr), to form a vacuum-baked internal metal surface ofthe container; iv) exposing the vacuum-baked internal metal surface ofthe container to a first fluid composition comprising asilicon-containing compound for a time sufficient to allow at least someof the silicon-containing compound to react with oxygen-containingcompounds (preferably selected from the group consisting of moisture,molecular oxygen, metal oxides, and mixtures thereof) present to form asilicon-treated surface on at least some of the vacuum-baked internalmetal surface of the container, the silicon-containing compoundpreferably selected from the group consisting of compounds within thegeneral formula (II); v) evacuating the container for a time sufficientto remove substantially all of the silicon-containing compound(s) thathas not reacted with the oxygen-containing compounds to form thesilicon-treated surface; vi) exposing the silicon-treated surface to asecond fluid composition, the second fluid composition comprising areactive gas having a concentration that is greater than an intendedreactive gas concentration of the article of manufacture; vii)evacuating the container for a time sufficient to remove just enough ofthe second fluid composition to enable maintenance of an increasedshelf-life, low concentration reactive gas at the intended concentrationin the container; and viii) combining at least a portion of the reducedmoisture reactive gas with at least a portion of the reduced moisturematrix gas to form an intended gas composition in the container.
 23. Themethod of claim 22 wherein the silicon-containing compound is selectedfrom the group consisting of silane, methylsilane, dimethylsilane,trimethylsilane and tetramethylsilane.
 24. The method of claim 22wherein the second fluid composition has a concentration of reactive gasat least 10 times the intended reactive gas concentration of themanufactured product.
 25. The method of claim 22 wherein steps iv) andv) are repeated prior to step vi).
 26. The method of claim 22 whereinthe metal surface is cleaned prior to step iii).
 27. The method of claim22 wherein the concentration of the silicon-containing compound used instep vi) ranges from about 100 ppm to 100 percent.
 28. The method ofclaim 22 wherein during step vii) the second composition is heated to atemperature of not more than 75° C.
 29. The method of claim 22 whereinthe container is a gas cylinder having an attached cylinder valve, andthe cylinder valve is removed prior to step iv).
 30. The method of claim22 wherein after steps i)-vi) are completed, preferably at very hightemperatures for steps iv) and vi), the cylinder valve is reattached,and the process steps iv)-vi) are repeated, but steps iv) and vi) takeplace at not more than 75° C.
 31. The method of claim 22 wherein themoisture concentration of the intended gas composition is no more than0.1 times the starting fluid composition water concentration.
 32. Themethod of claim 22 wherein the moisture concentration of the intendedgas composition is no more than 0.01 times the starting fluidcomposition water concentration.
 33. The method of claim 22 wherein themoisture concentration of the intended gas composition is no more than0.001 times the starting moisture concentration.
 34. The method of claim22 wherein acid gas-resistant molecular sieve is selected from the groupconsisting of molecular sieves having an effective pore size rangingfrom about 1 Angstrom up to about 10 Angstroms.
 35. The method of claim22 wherein the acid gas-resistant molecular sieve is selected from thegroup consisting of molecular sieves having an effective pore sizeranging from about 3 to about 8 Angstroms.
 36. The method of claim 22wherein the means for moisture reduction to form the reduced moisturematrix gas are selected from naturally occurring zeolites and syntheticzeolites.
 37. The method of claim 36 wherein the synthetic zeolite isselected from the group consisting of Zeolite X, Zeolite Y, Zeolite A,Zeolite B, Zeolite D, Zeolite E, Zeolite F, Zeolite H, Zeolite J,Zeolite L, Zeolite M, Zeolite O, Zeolite Q, Zeolite S, Zeolite T,Zeolite W, Zeolite Z, Zeolite Omega, ZK-4HJ type zeolites, alpha betatype zeolites, ZSM-type zeolites, and mixtures thereof.
 38. The methodof claim 36 wherein the naturally occurring zeolite is selected from thegroup consisting of faujasite, mordenite, clinoptilote, chabazite,analcite, erionite, as well as levynite, dachiardite, paulingite,noselite, ferriorite, heulandite, scolccite, stibite, harmotome,phillipsite, brewsterite, flarite, datolite, gmelinite, caumnite,leucite, lazurite, scaplite, mesolite, ptholite, nepheline, matrolite,offretite and sodalite.
 39. The method of claim 22 wherein the acid-gasresistant molecular sieve is zeolite AW300.